media-export: Use proper iso8601 date format

https://bugzilla.gnome.org/show_bug.cgi?id=702231
server: Fix time-seek on full-range seeks

https://bugzilla.gnome.org/show_bug.cgi?id=702262
server: Use object returned from server in CreateObject

https://bugzilla.gnome.org/show_bug.cgi?id=702743
server: Drop dlna: ns attributes on UpdateObject

We cannot validate them and the UpdateObject action fails because of
that, so we walk the node and remove all those attributes.

https://bugzilla.gnome.org/show_bug.cgi?id=701637
server,media-export: Use object.container

We used to use object.container.storageFolder for XBox 360 compatibility but
DLNA doesn't like that.

https://bugzilla.gnome.org/show_bug.cgi?id=702258
media-export: Use DLNA-compliant createClass

DLNA does not like upnp:createClass other than object.container for
containers. So we use that and use the possibility to "upgrade" the
object's class upon creation.

https://bugzilla.gnome.org/show_bug.cgi?id=702258
media-export: Allow reference creation everywhere

https://bugzilla.gnome.org/show_bug.cgi?id=702083
server: Fix error codes for CreateReference

https://bugzilla.gnome.org/show_bug.cgi?id=702083
Updated Spanish translation
server: Fix UPnP Error codes

CreateObject, UpdateObject and DestroyObject UPnP Actions were using
slightly wrong error codes.

https://bugzilla.gnome.org/show_bug.cgi?id=703140
Updated Spanish translation